787 research outputs found
Computation of the Chiral Anomaly in the Bulk Quantization
The bulk quantization method is used for regularizing a conventional four
dimensional theory of massless fermions coupled to an external non-Abelian
gauge field and for subsequently evaluating the associated Ward identity. As a
result one obtains the well-known chiral anomaly.Comment: 19 page
A light-cone approach to three-point functions in AdS_5 x S^5
We consider worldsheet correlation functions for strings in AdS_5 x S^5 using
a light-cone gauge for the worldsheet theory. We compute the saddle-point
approximation to three-point functions of BMN vertex operators, all with large
charges, by explicitly finding the intersection of three euclidean BMN strings.
We repeat this calculation for non-BPS circular winding strings extended along
a great circle of the S^5, though in this case the appropriate form of the
vertex operator is uncertain. Furthermore, we compute the spectrum of
fluctuations about euclidean BMN strings for generic boundary conditions, and
show that the spectrum depends only on the total charge and not the details of
the string configuration. We extend our considerations to include near-BMN
vertex operators and through the evaluation of the string path integral make
contact with the light-cone string field theory calculations of gauge theory
three-point structure constants.Comment: 42 pages, 2 figures; v2: typos corrected, references added; v3:
significant changes in section 7, in particular corrected saddle point for
three-point functio
Worldsheet Form Factors in AdS/CFT
We formulate a set of consistency conditions appropriate to worldsheet form
factors in the massive, integrable but non-relativistic, light-cone gauge fixed
AdS(5) x S**5 string theory. We then perturbatively verify that these
conditions hold, at tree level in the near-plane-wave limit and to one loop in
the near-flat (Maldacena-Swanson) limit, for a number of specific cases. We
further study the form factors in the weakly coupled dual description,
verifying that the relevant conditions naturally hold for the one-loop
Heisenberg spin-chain. Finally, we note that the near-plane-wave expressions
for the form factors, when further expanded in small momentum or, equivalently,
large charge density, reproduce the thermodynamic limit of the spin-chain
results at leading order.Comment: 30 pages, 12 figures, v3: typos fixed, improved discussion of bound
states and bound state axio
World-sheet scattering in AdS_5 x S^5 at two loops
We study the AdS_5 x S^5 sigma-model truncated to the near-flat-space limit
to two-loops in perturbation theory. In addition to extending previously known
one-loop results to the full SU(2|2)^2 S-matrix we calculate the two-loop
correction to the dispersion relation and then compute the complete two-loop
S-matrix. The result of the perturbative calculation can be compared with the
appropriate limit of the conjectured S-matrix for the full theory and complete
agreement is found.Comment: 26pages, 3 figure
The Perfect Atom: Bound States of Supersymmetric Quantum Electrodynamics
We study hydrogen-like atoms in N=1 supersymmetric quantum electrodynamics
with an electronic and a muonic family. These atoms are bound states of an
anti-muon and an electron or their superpartners. The exchange of a photino
converts different bound states into each other. We determine the energy
eigenstates and calculate the spectrum to fourth order in the fine structure
constant. A difference between these perfect atoms and non-supersymmetric ones
is the absence of hyperfine structure. We organize the eigenstates into super
multiplets of the underlying symmetry algebra.Comment: 30 pages, 2 figures. v2: mistake associated with gauge choice fixed,
references added. v3: comment about super-positronium added, published
versio
On the breakdown of perturbative integrability in large N matrix models
We study the perturbative integrability of the planar sector of a massive
SU(N) matrix quantum mechanical theory with global SO(6) invariance and
Yang-Mills-like interaction. This model arises as a consistent truncation of
maximally supersymmetric Yang-Mills theory on a three-sphere to the lowest
modes of the scalar fields. In fact, our studies mimic the current
investigations concerning the integrability properties of this gauge theory.
Like in the field theory we can prove the planar integrability of the SO(6)
model at first perturbative order. At higher orders we restrict ourselves to
the widely studied SU(2) subsector spanned by two complexified scalar fields of
the theory. We show that our toy model satisfies all commonly studied
integrability requirements such as degeneracies in the spectrum, existence of
conserved charges and factorized scattering up to third perturbative order.
These are the same qualitative features as the ones found in super Yang-Mills
theory, which were enough to conjecture the all-loop integrability of that
theory. For the SO(6) model, however, we show that these properties are not
sufficient to predict higher loop integrability. In fact, we explicitly
demonstrate the breakdown of perturbative integrability at fourth order.Comment: 27 page
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